Diocese in Spain, suffragan of Toledo; bounded on the north by Soria, on the east by Saragossa and Teruel, on the south by Cuenca, and on the west by Guadalajara and Segovia. It lies in the civil provinces of Guadalajara, Segovia, Soria, and Saragossa. Its episcopal city has a population of 5000. The site of the ancient Segoncia, now called Villavieja, is at half a league distant from the present Sigüenza; Livy speaks of the town in treating of the wars of Cato with the Celtiberians. The diocese is very ancient: the fictitious chronicles pretended that St. Sacerdos of Limoges had been its bishop; but, apart from these fables, we fimd Protogenes as Bishop of Sigüenza at the Third Council of Toledo, and again the same Protogenes at Gundemar's council in 610; Ilsidclus assisted at the fourth, fifth, and sixth councils; Wideric, at the seventh to the tenth; Egica, at the eleventh; Ela, at the twelfth, thirteenth, and fourteenth; Gunderic, at the fifteenth and sixteenth. The succession of bishops continued under the Arab domination: after St. Eulogius, in 851, we find there Sisemund, a man of great sagacity. But later on Sigüenza was so completely depopulated that it does not appear among the cities conquered by Alfonso VI when he subdued all this region. The first bishop of Sigüenza, after it had been repeopled, was Bernardo, a native of Agen, who had been "capisol" (caput schola - schoolmaster) of Toledo; he rebuilt the church and consecrated it on the Feast of St. Stephen, 1123, and placed in it a chapter of canons regular. He died Bishop-elect of Santiago. On 14 March, 1140, Alfonso VII granted the bishop the lordship of Sigüenza, which his successors retained until the fourteenth century.

After the long episcopate of Bernardo, Pedro succeeded, and was succeeded by Cerebruno, who began the building of the new cathedral. Jocelin, an Englishman, was present with the king at the conquest of Cuenca; he was succeeded by Arderico, who was transferred to Palencia; Martin de Hinojosa, the holy Abbot of Huerta, abdicated the see in 1192, and was succeeded by Rodrigo.

Sigüenza took a large part in the civil wars of the thirteenth and fourteenth centuries. The fortress palace of the bishops was captured in 1297 by the partisans of the Infantes de la Cerda, and in 1355 it was the prison of the unhappy Blanche of Bourbon, consort of Pedro the Cruel. In 1465 Diego López of Madrid, having usurped the mitre, fortified himself there. Pedro Gonzalez de Mendoza, the Cardinal of Spain, held this diocese together with that of Toledo, and enriched his relations by providing establishments for them at Sigüenza. His successor, Cardinal Bernardino de Carvajal, was dispossessed, as a schismatic by Julius II, for his share in the Conciliabulum of Pisa. After that Garcia de Loaisa, Fernando Valdés, Pedro Paeheco, and others held this wealthy see. The castle-palace, modified in various ways, suffered much from the storms of civil war, and was restored by Joaquin Fernandez Cortina, who was bishop from 1848, and the restoration was continued by Bishop Gomez Salazar (1876-79).

The cathedral is a very massive Gothic edifice of ashlar stone. Its façade has three doors, with a railed court in front. At the sides rise two square towers, 164 feet high, with merlons topped with large balls; these towers are connected by a balustrade which crowns the facade, the work of Bishop Herrera in the eighteenth century. The interior is divided into three Gothic naves. The main choir begins in the transept with a Renaissance altar built by order of Bishop Mateo de Burgos. In the transept is the Chapel of St. Librada, patroness of the city, with a splendid reredos and the relies of the saint, all constructed at the expense of Bishop Fadrique de Portugal, who is buried there. What is now the Chapel of St. Catherine was dedicated to St. Thomas of Canterbury by the English Bishop Jocelin, who came with Queen Leonora. Cardinal Mendoza is interred in the main choir. Beyond the choir proper, which is situated in the centre, there is the sumptuous altar of Nuestra Señora la Mayor. Connected with the church is a beautiful Florid Gothic cloister, the work of Bernardino de Carvajal. The rich tabernacle, with its golden monstrance, was given by Cardinal Mendoza. The chapter house contains many excellent paintings. It is not known with any certainty at what period this church was begun, though it appears to date from the end of the twelfth century. The image of Nuestra Señora la Mayor, to whom the church is dedicated, dates from the end of the twelfth century; it was taken to the retro-choir in the fifteenth century, the Assumption being substituted for it on the high altar.

The Conciliar Seminary of San Bartolomé is due to Bishop Bartolomé Santos de Risoba (1651). There is a smaller seminary, that of the Immaculate Conception, and a college. The College of San Antonio el Grande is a beautiful building. It was formerly a university, founded in 1476 by the wealthy; Juan López de Medina, archdeacon of Almázán, but its prosperity was hindered by the foundation of the University of Alcalá; in 1770 it was reduced to a few chairs of philosophy and theology, and was suppressed in 1837. Worthy of mention are the ancient hermitage of Nuestra Señora, which, according to tradition, had been originally the pro-cathedral; the Humilladero, a small Gothic hermitage; the Churrigueresque convent of the Franciscans; the modern convent the Ursulines, which was formerly the home of the choir boys; the hospital of the military barracks; and the Hieronymite college.

The building of the College of San Antonio Portaceli of Sigüenza, Spain, which was later transformed into a university, was begun in 1476. Its founder was Don Juan López de Medina, archdeacon of Almázán, canon of Toledo, and vicar-general of Sigüenza. The Bull ratifying the foundation, approving the benefices, etc., was granted by Sixtus IV in 1483, and courses were opened in theology, canon law, and arts. By a Bull of Innocent VIII in 1489, the university was created, with powers to confer the degrees of bachelor, licentiate, and doctor; the college was thus transformed into a university. A Bull issued by Paul III extended the course in theology, and, during the rectorate of Maestro Velosillo, the chairs of physics were created, while a Bull of Julius II established the faculties of law and of medicine. Among the professors were Pedro Ciruelo, who enhanced the prestige of the university as a centre of learning; Don Franeiseo Delgado, Bishop of Lugo, who was rector, and under whom the university reached its period of greatest splendour; Don Fernando Velosillo, rector and professor, was sent by Philip II to the Council of Trent. There were also present at that council, as theologians, Don Antonio Torres, first Bishop of the Canary Islands, and Senor Torro, both professors of this university; Don Pedro Guerrero, Archbishop of Granada; the famous Cuesta; Tricio and Francisco Alvarez, Bishop of Sigüenza. It is thus evident that the influence of the University of Sigüenza in Church and State was considerable in the last years of the fifteenth century and the first years of the sixteenth; thereafter it fell into decay. It was suppressed in 1837.